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• What do you call a generalized (non-GUI-related) "Model-View-Controller" architecture?

  - by dcuccia

  I am currently refactoring code that coordinates multiple hardware components for data acquisition, and feeling a bit like I'm recreating the wheel. In particular, an MVC-like pattern seems to be emerging. Except, this has nothing to do with a GUI and I'm worried that I'm forcing this particular pattern where another might be more appropriate. Here's my scenario: Individual hardware "component" classes obey interface contracts for each hardware type. Previously, component instances were orchestrated by a single monolithic InstrumentController class, which relied heavily on configuration + branching logic for executing a specific acquisition sequence. After an iteration, I have a separate controller for each component, with these controllers all managed by a small InstrumentControllerBase (or its derivatives). The composite system will receive "input" either programmatically or via inter-hardware component triggering - in either case these interactions are routed to, and handled by, the appropriate controller. So, I have something that feels MVC-esque, but I don't know if that's because I'm forcing the point. With little direct MVC experience in application development, it's hard to know if I'm just trying to make my scenario fit MVC, where another pattern might be a good alternative or complimentary. My problem is, search results and wiki documentation of these family of patterns seems to immediately drop me into GUI-specific discussions. I understand "M means Model data and the V means View" - but do you call the superset pattern? Component-Commander-Controller? Whence can I exhume examples exemplary?

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• Parallelizing L2S Entity Retrieval

  - by MarkB

  Assuming a typical domain entity approach with SQL Server and a dbml/L2S DAL with a logic layer on top of that: In situations where lazy loading is not an option, I have settled on a convention where getting a list of entities does not also get each item's child entities (no loading), but getting a single entity does (eager loading). Since getting a single entity also gets children, it causes a cascading effect in which each child then gets its children too. This sounds bad, but as long as the model is not too deep, I usually don't see performance problems that outweigh the benefits of the ease of use. So if I want to get a list in which each of the items is fully hydrated with children, I combine the GetList and GetItem methods. So I'll get a list and then loop through it getting each item with the full cascade. Even this is generally acceptable in many of the projects I've worked on - but I have recently encountered situations with larger models and/or more data in which it needs to be more efficient. I've found that partitioning the loop and executing it on multiple threads yields excellent results. In my first experiment with a list of 50 items from one particular project, I did 5 threads of 10 items each and got a 3X improvement in time. Of course, the mileage will vary depending on the project but all else being equal this is clearly a big opportunity. However, before I go further, I was wondering what others have done that have already been through this. What are some good approaches to parallelizing this type of thing?

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• Tree iterator, can you optimize this any further?

  - by Ron

  As a follow up to my original question about a small piece of this code I decided to ask a follow up to see if you can do better then what we came up with so far. The code below iterates over a binary tree (left/right = child/next ). I do believe there is room for one less conditional in here (the down boolean). The fastest answer wins! The cnt statement can be multiple statements so lets make sure this appears only once The child() and next() member functions are about 30x as slow as the hasChild() and hasNext() operations. Keep it iterative <-- dropped this requirement as the recursive solution presented was faster. This is C++ code visit order of the nodes must stay as they are in the example below. ( hit parents first then the children then the 'next' nodes). BaseNodePtr is a boost::shared_ptr as thus assignments are slow, avoid any temporary BaseNodePtr variables. Currently this code takes 5897ms to visit 62200000 nodes in a test tree, calling this function 200,000 times. void processTree (BaseNodePtr current, unsigned int & cnt ) { bool down = true; while ( true ) { if ( down ) { while (true) { cnt++; // this can/will be multiple statesments if (!current->hasChild()) break; current = current->child(); } } if ( current->hasNext() ) { down = true; current = current->next(); } else { down = false; current = current->parent(); if (!current) return; // done. } } }

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• Matching Class arrays

  - by frinkz

  I'm writing a routine to invoke methods, found by a name and an array of parameter Class values Matching the Method by getName works, but when trying to match the given Class[] for parameters, and Method.getParameterTypes(), I'm having trouble. I assumed that this would work: Class[] searchParams = new Class[] { float.class, String.class }; Class[] methodParams = m.getParameterTypes(); if(methodParams == searchParams) { m.invoke(this, paramValues); } But apparantly not - m.invoke is never reached. I've checked, and methodParams gives the same classes as searchParams. The code below works, and picks the right method, but it seems like a very dirty way of doing things, I'm sure I'm missing something obvious. Class[] searchParams = new Class[] { float.class, String.class }; Class[] methodParams = m.getParameterTypes(); boolean isMatch = true; for(int i = 0; i < searchParams.length; i++) { if(!searchParams.getClass().equals(methodParams.getClass())) { isMatch = false; } } if(isMatch) { m.invoke(this, paramValues); }

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• Relating text fields to check boxes in Java

  - by Finzz

  This program requires the user to login and request a database to access. The program then gets a connection object, searches through the database storing the column names into a vector for later use. The problem comes with implementing text fields to allow the user to search for specific values within the database. I can get the check boxes and text fields to appear using a gridlayout and add them to a panel. How do I relate the text fields to their appropriate check box? I've tried adding them to a vector, but then they can't also be added to the panel as well. I've searched for a way to name the text fields as the loop cycles through the column names, but it seems impossible to do without having them declared ahead of time. This can't be done either, as it's impossible to determine the attributes that the user will request. I just need to be able to know the names of the text fields so I can test to see if the user entered information and perform the necessary logic. Let me know if you have to see the rest of the code to give an answer, but hopefully you get the general idea of what I'm trying to accomplish. Picture of UI: try { ResultSet r2 = con.getMetaData().getColumns("", "", rb.getText(), ""); colNames1 = new Vector<String>(); columns1 = new Vector<JCheckBox>(); while (r2.next()) { colNames1.add(r2.getString(4)); JCheckBox cb = new JCheckBox(r2.getString(4)); JTextField tf = new JTextField(10); columns1.add(cb); p3.add(cb); p3.add(tf); } }

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• Prolog, check if term is power of 2

  - by Riku

  i have written following code, which should work with my logic, but it does not. I should check if given term is power of two. For example s(s(s(nul))) should return false, s(s(s(s(nul))) should return true. substractWhileY(X,0,rezult). substractWhileY(s(X),Y,rezult):- Y > 0, number is 1, substractWhileY(X,Y - number, rezult). degreeOftwo(X):- substractWhileY(X,2,rezult), pagalba(X, 2, rezult). calculateAnswer(X, currentCounter, currentValue):- currentCounter is currentCounter * 2, substractWhileY(currentValue, currentCounter , rezult), rezult\= null, calculateAnswer(X, currentCounter , rezult). My idea was to check if given therm is degree of any two and if it is not than it is not the degree of two. With numbers it should work like this. For example i give number 8. First time it checks if 8 - 2 = 0. second time if 8 - 4 = 0. third time if 8 - 8 = 0. so the 8 id power of two. Maybe other solution would work better, so thanks for any help.

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• How to use App.Xaml's ResourseDictionaries with own entry point

  - by Polaris

  Hello friends. I created some logic for singleInstance application and I must to use my own entry point (not App.xaml) for Application. I have some styles in App.xaml which now is not working. How can I use this ResourceDictionaries from my App.xaml for entire project in my situation? My class for manage Application Startup public class SingleInstanceManager : WindowsFormsApplicationBase { App app; public SingleInstanceManager() { this.IsSingleInstance = true; } protected override bool OnStartup(Microsoft.VisualBasic.ApplicationServices.StartupEventArgs e) { try { // First time app is launched app = new App(); App.Current.Properties["rcID"] = e.CommandLine; //IntroLibrary.OpenDocumentFromNotify(); app.Run(); return false; } catch (Exception ex) { MessageBox.Show(ex.Message); return false; } } protected override void OnStartupNextInstance(StartupNextInstanceEventArgs eventArgs) { // Subsequent launches base.OnStartupNextInstance(eventArgs); Intro win = (Intro)app.MainWindow; if (eventArgs != null) { App.Current.Properties["rcID"] = eventArgs.CommandLine[0]; } IntroLibrary.OpenDocumentFromNotify(); app.Activate(); } } and my own Entry Point: public class EntryPoint { [STAThread] public static void Main(string[] args) { SingleInstanceManager manager = new SingleInstanceManager(); manager.Run(args); } } And my App.Xaml code behind: public partial class App : Application { protected override void OnStartup(System.Windows.StartupEventArgs e) { base.OnStartup(e); // Create and show the application's main window Intro window = new Intro(); window.Show(); } public void Activate() { // Reactivate application's main window this.MainWindow.Activate(); } } And my App.xaml has some code which decribe ResourceDictionaries which doesnt work. Why?

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• .NET 4 ... Parallel.ForEach() question

  - by CirrusFlyer

  I understand that the new TPL (Task Parallel Library) has implemented the Parallel.ForEach() such that it works with "expressed parallelism." Meaning, it does not guarantee that your delegates will run in multiple threads, but rather it checks to see if the host platform has multiple cores, and if true, only then does it distribute the work across the cores (essentially 1 thread per core). If the host system does not have multiple cores (getting harder and harder to find such a computer) then it will run your code sequenceally like a "regular" foreach loop would. Pretty cool stuff, frankly. Normally I would do something like the following to place my long running operation on a background thread from the ThreadPool: ThreadPool.QueueUserWorkItem( new WaitCallback(targetMethod), new Object2PassIn() ); In a situation whereby the host computer only has a single core does the TPL's Parallel.ForEach() automatically place the invocation on a background thread? Or, should I manaully invoke any TPL calls from a background thead so that if I am executing from a single core computer at least that logic will be off of the GUI's dispatching thread? My concern is if I leave the TPL in charge of all this I want to ensure if it determines it's a single core box that it still marshalls the code that's inside of the Parallel.ForEach() loop on to a background thread like I would have done, so as to not block my GUI. Thanks for any thoughts or advice you may have ...

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• Starting a process synchronously, and "streaming" the output

  - by Benjol

  I'm looking at trying to start a process from F#, wait till it's finished, but also read it's output progressively. Is this the right/best way to do it? (In my case I'm trying to execute git commands, but that is tangential to the question) let gitexecute (logger:string->unit) cmd = let procStartInfo = new ProcessStartInfo(@"C:\Program Files\Git\bin\git.exe", cmd) // Redirect to the Process.StandardOutput StreamReader. procStartInfo.RedirectStandardOutput <- true procStartInfo.UseShellExecute <- false; // Do not create the black window. procStartInfo.CreateNoWindow <- true; // Create a process, assign its ProcessStartInfo and start it let proc = new Process(); proc.StartInfo <- procStartInfo; proc.Start() |> ignore // Get the output into a string while not proc.StandardOutput.EndOfStream do proc.StandardOutput.ReadLine() |> logger What I don't understand is how the proc.Start() can return a boolean and also be asynchronous enough for me to get the output out of the while progressively. Unfortunately, I don't currently have a large enough repository - or slow enough machine, to be able to tell what order things are happening in...

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• How to show alert in a jsp from a servlet and then redirect to another jsp?

  - by Xaul Omar Tobar

  I tried this but does not display the message only redirects login.jsp <form method="post" action="Login_Servlet" > <input name="idUsuario" type="text"/> <input name="password" type="password" /> <button type="submit">Entrar</button> </form> Login_Servlet response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); String userid= request.getParameter("idUser"); String password = request.getParameter("password"); Login_Service login_Service = new Login_Service(); boolean result = login_Servicio.aut(userid, password); Usuario user = login_Servicio.getUsuariosByUsuario(userid); if(result == true){ request.getSession().setAttribute("user", user); response.sendRedirect("vistas/Inicio.jsp"); } else{ out.println("<script type=\"text/javascript\">"); out.println("alert('User or password incorrect');"); out.println("</script>"); response.sendRedirect("index.jsp"); } Is it possible to display a message like this? if so I'm doing wrong?

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• How to add clear option to this whiteboard?

  - by swift

  i have to add clear screen option to my whiteboard application, usual procedure is to draw a fill rect to the sizeof the image. But in my app i have transparent panels added one above the other i.e as layers, if i follow the usual procedure the drawing from the underlying panel wont be visible. please tell me any logic to do this. public void createFrame() { JFrame frame = new JFrame(); JLayeredPane layerpane=frame.getLayeredPane(); board= new Whiteboard(client); //board is a transparent panel // tranparent image: board.image = new BufferedImage(590,690, BufferedImage.TYPE_INT_ARGB); board.setBounds(74,23,590,690); board.setImage(image); virtualboard.setImage(image); //virtualboardboard is a transparent panel virtualboard.setBounds(74,23,590,690); JPanel background=new JPanel(); background.setBackground(Color.white); background.setBounds(74,25,590,685); layerpane.add(board,new Integer(5)); layerpane.add(virtualboard,new Integer(4));//Panel where remote user draws layerpane.add(background,new Integer(3)); layerpane.add(board.colourButtons(),new Integer(2)); layerpane.add(board.shapeButtons(),new Integer(1)); layerpane.add(board.createEmptyPanel(),new Integer(0)); }

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• How can i design a DB where the user can define the fields and types of a detail table in a M-D rela

  - by Simon

  My application has one table called 'events' and each event has approx 30 standard fields, but also user defined fields that could be any name or type, in an 'eventdata' table. Users can define these event data tables, by specifying x number of fields (either text/double/datetime/boolean) and the names of these fields. This 'eventdata' (table) can be different for each 'event'. My current approach is to create a lookup table for the definitions. So if i need to query all 'event' and 'eventdata' per record, i do so in a M-D relaitionship using two queries (i.e. select * from events, then for each record in 'events', select * from 'some table'). Is there a better approach to doing this? I have implemented this so far, but most of my queries require two distinct calls to the DB - i cannot simply join my master 'events' table with different 'eventdata' tables for each record in in 'events'. I guess my main question is: can i join my master table with different detail tables for each record? E.g. SELECT E.*, E.Tablename FROM events E LEFT JOIN 'E.tablename' T ON E._ID = T.ID If not, is there a better way to design my database considering i have no idea on how many user defined fields there may be and what type they will be.

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• steam condenser java errors

  - by w0rm

  I've been working on a little project involving Steam Condenser, a Steam API written in Java, but I haven't been able to actually do anything with it. I'll explain. This is what the wiki tells me: SteamId id = new SteamId("demomenz"); GameStats stats = id.getGameStats("tf2"); List achievements = stats.getAchievements(); The problem is, eclipse doesn't like it apparently, as it spits out this error: The constructor SteamId(String) is undefined and it gives me the option to change it to: SteamId id = new SteamId("demomenz", false); But at this point a different error comes out: The constructor SteamId(Object, boolean) is not visible So, I'm assuming this function is internal to the API, and should not be called from the outside. If anyone is familiar with this, or has a clue on why I'm getting this error (I'm fairly new to Java development), an answer would be greatly appreciated. UPDATE: The constructor SteamId(String) is undefined This is if I use SteamId.create(ConvertedID); (ConvertedID is a String containing the Steam64 ID). At this point I believe this API is not that well written, at least for java. Any other idea?

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• Wrapping a Flash/AS3 Sprite as a Flex MXML component

  - by John

  For my game, I am making the main game view as a plain Flash/AS3 class, something like: public class GameArena extends Sprite This is simply a big rectangle in which game objects are drawn, so no need for fancy UI and I want to keep the main game engine Flex-free so I can use Sprites rather than heavier Flex components. However for the entire game/app, I do still want to use Flex for GUI/layout. So I thought I could create a Flex class subclassing UIComponent, which has a GameView object as a child... now I can use this in MXML as a standard Flex component. e.g. public class ArenaView extends UIComponent { public var gameArena:GameArena; override protected function createChildren():void { super.createChildren(); if (!gameArena) { gameArena = new GameArena(); gameArena.width = 200; gameArena.height = 200; addChild(gameArena); } } } Then I have a simple line in my main App MXML like: <logic:Arena x="0" y="0" width="50%" height="100%" name="TestArenaPanel" /> But so far while my code compiles, the Flash class isn't getting rendered. Maybe it's something simple, but I wanted to ask if this is a reasonable approach, or there is something better? BTW: I've had the "should Flex be used" conversation many times. If you want to discuss that please do so in comments, but keep answers on topic.

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• Checking servlet session attribute value in jsp file

  - by Marta

  I have a no framework java application. It consists of jsp files for view and servlets for the business logic. I must set the user session is the servlet with a firstName parameter. In the jsp file, I need to check if my firstName parameter has a value or not. If the firstName parameter is set, I need to display some html in the jsp file. If it is not set, I need to display different html in the jsp file. Servlet.java: HttpSession session = request.getSession(); session.setAttribute("firstName", customer.getFristName()); String url = "/index.jsp"; RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(url); dispatcher.forward(request, response); header.jsp: // Between the <p> tags bellow I need to put some HTML with the following rules // If firstName exist: Hello ${firstName} <a href="logout.jsp">Log out</a> // Else: <a href="login.jsp">Login</a> or <a href="register.jsp">Register</a> <p class="credentials" id="cr"></p> What would be the best way to do this? Any help is much appreciated! Thank you in advance. -Marta

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• Ruby & ActiveRecord: referring to integer fields by (uniquely mapped) strings

  - by JP

  While its not my application a simple way to explain my problem is to assume I'm running a URL shortener. Rather than attempt to try and figure out what the next string I should use as the unique section of the URL, I just index all my URLs by integer and map the numbers to strings behind the scenes, essentially just changing the base of the number to, let's say, 62: a-z + A-Z + 0-9. In ActiveRecord I can easily alter the reader for the url_id field so that it returns my base 62 string instead of the number being stored in the database: class Short < ActiveRecord::Base def url_id i = read_attribute(:convo) return '0' if i == 0 s = '' while i > 0 s << CHARS[i.modulo(62)] i /= 62 end s end end but is there a way to tell ActiveRecord to accept Short.find(:first,:conditions=>{:url_id=>'Ab7'}), ie. putting the 'decoding' logic into my Short ActiveRecord class? I guess I could define my own def self.find_by_unique_string(string), but that feels like cheating somehow! Thanks!

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• Ordering .each results in the view...

  - by bgadoci

  I am wondering if it is possible to dictate the order (i.e. :order = 'created_at DESC') within the view. I realize that logic in the view is not ideal but I seem to be having some problems locating where to affect this output. For instance, here is my code: <% @user.questions.each do |question| %> <%= link_to_unless_current h (question.title), question %> Created about <%= time_ago_in_words h(question.created_at) %> ago Updated about <%= time_ago_in_words h(question.updated_at) %> ago <%= link_to 'Edit', edit_question_path(question) %> | <%= link_to 'Destroy', question, :confirm => 'Are you sure?', :method => :delete %> <% end %> In my QuestionsController I have the following index action but it is not affecting the output from the code above. class QuestionsController < ApplicationController def index @questions = Question.all(:order => 'created_at DESC', :limit => 20) respond_to do |format| format.html # index.html.erb format.xml { render :xml => @questions } end end end

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• Dependencyproperty doesn't have value on load

  - by Jakob

  My problem is this, I have a UC called profile that contains another UC called FollowImageControl. In my Profile.xaml i declaretively bind a property of FollowImageControl called FollowerId to a CurrentUserId from Profile.xaml.cs. Problem is that I CurrentUserId is assigned in Profile.xaml.cs; the Profile.xaml code-behind. This means that I do not initially get the FollowerId. I have these methods in the FollowImageControl.xaml.cs: public static readonly DependencyProperty _followUserId = DependencyProperty.Register("FollowUserId", typeof(Guid), typeof(FollowImageControl), null); public Guid FollowUserId { get { return (Guid)GetValue(_followUserId); } set { SetValue(_followUserId, value); } } public FollowImageControl() { // Required to initialize variables InitializeComponent(); LoggedInUserId = WebContext.Current.User.UserId; var ctx = new NotesDomainContext(); if (ctx.IsFollowingUser(LoggedInUserId, FollowUserId).Value) SwitchToDelete.Begin(); } private void AddImg_MouseLeftButtonDown(object sender, MouseButtonEventArgs e) { if (LoggedInUserId != FollowUserId) { var ctx = new NotesDomainContext(); ctx.FollowUser(FollowUserId, LoggedInUserId); ctx.SubmitChanges(); } } THE WEIRD THING IS that when i insert breakpoints the FollowerUserId in FollowImageControl() is 0, but it has a value in AddImg_MouseLeftButtonDown, and there is no inbetween logic that sets the value of it. How is this??? Here's a little more code info: This is my binding from profile.xaml <internalCtrl:FollowImageControl FollowUserId="{Binding ElementName=ProfileCtrl, Path=CurrentUserId}" /> this is my constructor in profile.xaml.cs wherein the CurrentUserId is set public static readonly DependencyProperty _CurrentUserId = DependencyProperty.Register("CurrentUserId", typeof(Guid), typeof(Profile), null); public Guid CurrentUserId { get { return (Guid)GetValue(_CurrentUserId); } set { SetValue(_CurrentUserId, value); } } public Profile(Guid UserId) { CurrentUserId = UserId; InitializeComponent(); Loaded += new RoutedEventHandler(Profile_Loaded); } I'm seriously dumbfound that one minute the FollowerId has no value, and the next it holds the right, without me having changed the value in the code-behind.

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• Simulating a 2-level If-Else using RewriteCond

  - by hlissner

  Hi! I'm trying to get my head around RewriteCond, and want to rewrite any requests either to a static html page (if it exists), or to a specific index.php (so long as the requested file doesn't exist). To illustrate the logic: if HTTP_HOST is '(www\.)?mydomain.com' if file exists: "/default/static/{REQUEST_URI}.html", then rewrite .* to /default/static/{REQUEST_URI}.html else if file exists: {REQUEST_FILENAME}, then do not rewrite else rewrite .* to /default/index.php I don't seem to have much trouble doing it when I don't need to test for the HTTP_HOST. Ultimately, this one .htaccess file will be handling requests for several domains. I know I could get around this with vhosts, but I'd like to figure out how to do it this way. Here's where I am at now: RewriteCond %{HTTP_HOST} ^(www\.)?mydomain\.com$ [NC] RewriteCond /default/static/%{REQUEST_URI}.html -f RewriteRule . /default/static/%{REQUEST_URI}.html [L,NC] RewriteCond %{REQUEST_FILENAME} !-f RewriteRule . /default/index.php [L,QSA] I'm not too familiar with some of the other flags, will any of them be of use here (like chain|C, next|N or skip|S)? Thanks in advance! UPDATE: I've managed to do it, but would appreciate alternatives: RewriteEngine On RewriteRule ^(.+)/$ /$1 [L] RewriteCond %{HTTP_HOST} ^(domainA|domainB)\.com [NC] RewriteCond %{DOCUMENT_ROOT}/%1/static/%{REQUEST_URI}.html -f RewriteRule (.*)? /%1/static/$1.html [NC,L] RewriteCond %{HTTP_HOST} ^(domainA|domainB)\.com [NC] RewriteCond %{REQUEST_FILENAME} !-f RewriteRule .* /%1/index.php [L,QSA]

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• Many tables for many users?

  - by Seagull

  I am new to web programming, so excuse the ignorance... ;-) I have a web application that in many ways can be considered to be a multi-tenant environment. By this I mean that each user of the application gets their own 'custom' environment, with absolutely no interaction between those users. So far I have built the web application as a 'single user' environment. In other words, I haven't actually done anything to support multi-users, but only worked on the functionality I want from the app. Here is my problem... What's the best way to build a multi-user environment: All users point to the same 'core' backend. In other words, I build the logic to separate users via appropriate SQL queries (eg. select * from table where user='123' and attribute='456'). Each user points to a unique tablespace, which is built separately as they join the system. In this case I would simply generate ALL the relevant SQL tables per user, with some sort of suffix for the user. (eg. now a query would look like 'select * from table_ where attribute ='456'). In short, it's a difference between "select * from table where USER=" and "select * from table_USER".

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• What is a good "Error Checking" Pattern (Java)?

  - by Jack

  I'll explain what I mean by input error checking. Say you have a function doSomething(x). If the function completes successfully doSomething does something and returns nothing. However, if there are errors I'd like to be notified. That is what I mean by error checking. I'm looking for, in general, the best way to check for errors. I've thought of the following solutions, each with a potential problem. Flag error checking. If doSomething(x) completes successfully return null. Otherwise, it returns a boolean or an error string. Problem: Side effects. Throwing an exception. Throw an exception if doSomething(x) encounters an error. Problem: If you are performing error checking for parameters only, throwing an IllegalArgumentExceptionseems inappropriate. Validating input prior to function call. If the error checking is only meant for the parameters of the function, then you can call a validator function before calling the doSomething(x) function. Problem: What if a client of the class forgets to call the validator function before calling doSomething(x)? I often encounter this problem and any help or a point in the right direction would be much appreciated.

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• Confused about std::runtime_error vs. std::logic_error

  - by David Gladfelter

  I recently saw that the boost program_options library throws a logic_error if the command-line input was un-parsable. That challenged my assumptions about logic_error vs. runtime_error. I assumed that logic errors (logic_error and its derived classes) were problems that resulted from internal failures to adhere to program invariants, often in the form of illegal arguments to internal API's. In that sense they are largely equivalent to ASSERT's, but meant to be used in released code (unlike ASSERT's which are not usually compiled into released code.) They are useful in situations where it is infeasible to integrate separate software components in debug/test builds or the consequences of a failure are such that it is important to give runtime feedback about the invalid invariant condition to the user. Similarly, I thought that runtime_errors resulted exclusively from runtime conditions outside of the control of the programmer: I/O errors, invalid user input, etc. However, program_options is obviously heavily (primarily?) used as a means of parsing end-user input, so under my mental model it certainly should throw a runtime_error in the case of bad input. Where am I going wrong? Do you agree with the boost model of exception typing?

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• Passing values for method

  - by Kasun

  I beginner for programming. So can you please show me how to pass values for your compile() method. class CL { private const string clexe = @"cl.exe"; private const string exe = "Test.exe", file = "test.cpp"; private string args; public CL(String[] args) { this.args = String.Join(" ", args); this.args += (args.Length > 0 ? " " : "") + "/Fe" + exe + " " + file; } public Boolean Compile(String content, ref string errors) { //remove any old copies if (File.Exists(exe)) File.Delete(exe); if (File.Exists(file)) File.Delete(file); File.WriteAllText(file, content); Process proc = new Process(); proc.StartInfo.UseShellExecute = false; proc.StartInfo.RedirectStandardOutput = true; proc.StartInfo.RedirectStandardError = true; proc.StartInfo.FileName = clexe; proc.StartInfo.Arguments = this.args; proc.StartInfo.CreateNoWindow = true; proc.Start(); //errors += proc.StandardError.ReadToEnd(); errors += proc.StandardOutput.ReadToEnd(); proc.WaitForExit(); bool success = File.Exists(exe); return success; } }

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• Project Naming Convention Feedback Please

  - by Sam Striano

  I am creating a ASP.NET MVC 3 application using Entity Framework 4. I am using the Repository/Service Pattern and was looking for feedback. I currently have the following: MVC Application (GTG.dll) GTG GTG.Controllers GTG.ViewModels Business POCO's (GTG.Business.dll) This contains all business objects (Customer, Order, Invoice, etc...) EF Model/Repositories (GTG.Data.dll) GTG.Business (GTG.Context.tt) I used the Entity POCO Generator Templates. GTG.Data.Repositories Service Layer (GTG.Data.Services.dll) GTG.Data.Services - Contains all of the service objects, one per aggregate root. The following is a little sample code: Controller Namespace Controllers Public Class HomeController Inherits System.Web.Mvc.Controller Function Index() As ActionResult Return View(New Models.HomeViewModel) End Function End Class End Namespace Model Namespace Models Public Class HomeViewModel Private _Service As CustomerService Public Property Customers As List(Of Customer) Public Sub New() _Service = New CustomerService _Customers = _Service.GetCustomersByBusinessName("Striano") End Sub End Class End Namespace Service Public Class CustomerService Private _Repository As ICustomerRepository Public Sub New() _Repository = New CustomerRepository End Sub Function GetCustomerByID(ByVal ID As Integer) As Customer Return _Repository.GetByID(ID) End Function Function GetCustomersByBusinessName(ByVal Name As String) As List(Of Customer) Return _Repository.Query(Function(x) x.CompanyName.StartsWith(Name)).ToList End Function End Class Repository Namespace Data.Repositories Public Class CustomerRepository Implements ICustomerRepository Public Sub Add(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Add End Sub Public Sub Delete(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Delete End Sub Public Function GetByID(ByVal ID As Integer) As Business.Customer Implements IRepository(Of Business.Customer).GetByID Using db As New GTGContainer Return db.Customers.FirstOrDefault(Function(x) x.ID = ID) End Using End Function Public Function Query(ByVal Predicate As System.Linq.Expressions.Expression(Of System.Func(Of Business.Customer, Boolean))) As System.Linq.IQueryable(Of Business.Customer) Implements IRepository(Of Business.Customer).Query Using db As New GTGContainer Return db.Customers.Where(Predicate) End Using End Function Public Sub Save(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Save End Sub End Class End Namespace

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• Collision Detection (Ground & Slopes) in 2D Platform Game using Pygame Rects

  - by RedCap

  Hi, First off, I am not after any instructions on logic for collision detection; I get it. What I am trying to work out is the least complicated way to do this with Pygame using Sprites & Rects. I want to be able to check collisions for the Player against ground, walls & slopes. In theory it is quite straight forward, but I'm having difficulty because it seems like you cannot do this with one Rect. One Rect is simple enough to get you collisions in the X plane against walls. The same Rect could be used also be used in the Y plane against solids, but not with slopes - since with the collision routines in Pygame it checks the whole Rect (or mask), rather than perhaps just the bottom middle of the Rect. It seems in addition you need to have a number of "sprites" to check collisions with, that are 1x1 pixel in various places around the Player. What's the easiest way to do this, without having a bunch of 3, 4, or more separate "collision pixels" to check against slopes? Geoff

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